In order to assure efficient operation of drive systems employing crawler tracks, it is necessary that proper tension be maintained in the tracks. Incorrect tensioning of the crawler tracks accelerates their wear, and can even lead to loss of a track under some operating conditions. To accommodate proper tensioning of crawler tracks, most systems employ an idler wheel positioned at one end of each track. The idler is typically movable with respect to the carriage which carries the track in order to allow adjustment of track tension.
One commonly employed arrangement for adjusting track tension is the provision of a hydraulic cylinder or the like associated with the idler wheel, with the cylinder being adapted to receive pressurized hydraulic fluid or grease for tensioning of the crawler track. While such arrangements can be effective for adjusting track tension, they typically require relatively frequent addition of fluid to the tensioning hydraulic cylinder to accommodate lengthening of the track as it wears, and to replenish fluid which seeps from the tensioning cylinder. Because such arrangements usually require that a pump be manually fitted to each tensioning cylinder for addition of fluid, maintaining proper crawler track tension can be time consuming and inconvenient. Additionally, such arrangements usually have no provision for altering track tension during operation. While a suitable fluid pressure relief may be provided to prevent excessive track tension which can occur if an obstacle is encountered, such arrangements usually then require that the tensioning cylinder be repressurized before operation can continue.
In order to eliminate the need to manually pressurize the tensioning cylinders of a crawler track drive, arrangements have been developed which include a suitable hydraulic fluid pump and valving system for supplying pressurized fluid to the track tensioning cylinders. Although this may eliminate the need for an operator to repressurize each tensioning cylinder with a hand-held pump or the like, the provision of a specialized pressurizing arrangement increases the cost and complexity of the overall crawler drive system. Additionally, such specialized pressurizing arrangements generally are not responsive to the torque applied to the crawler track by the track drive motor. Because it has been determined that there is a direct desired correlation between torque applied to the track and the desired track tension, this is a further distinct disadvantage of such tensioning arrangements.